The present invention relates generally to cooling systems for heat-generating devices and, more particularly, to a spray cooling system and a method of using the spray cooling system to cool one or more semiconductor components (i.e., chips).
With the advent of semiconductor devices having increasingly large component densities, the removal of heat generated by these devices has become an increasingly challenging technical issue. Moreover, device miniaturization has led device designers to integrate previously separate components, such as those used to create a cache for a microprocessor, into the microprocessor die. This consolidation of devices has resulted in high CPU core power density, and extreme power dissipation requirements.
The use of boiling/vaporizing methods with inert cooling fluids provides cooling levels that can meet extreme cooling requirements. While pool boiling (i.e., submerging a chip in coolant) provides significant gains over traditional air cooling, spray cooling (i.e., spraying the chip with coolant) presently provides the highest heat dissipation levels for a heat-generating device such as a semiconductor chip. The best results are obtained when the coolant is uniformly sprayed over each area having a uniform dissipation requirement. The mass flow rate of sprayed coolant should be at a level such that the energy needed to vaporize the sprayed coolant matches the power dissipation requirements of the device.
With reference to FIG. 1, in single, high-dissipation, spray cooling system, an inert spray coolant from a reservoir 11 is preferably sprayed by a group of one or more sprayers 13 onto an aligned group of one or more chips 15 mounted on a printed circuit board 17. The coolant preferably evaporates, dissipating heat within the chip. The sprayers, the chips and the board are mounted within an evacuated and sealed case 19 fixed within a computer system. The sprayed coolant is typically gathered and cooled within a condenser 21, and then routed back to the reservoir by a pump 23. For semiconductor devices, low boiling point fluids such as 3M(copyright) FC-72 (FED. CIR.-72, i.e., FLUORINERT(copyright), sold by 3M(copyright) Corporation), 3M""s Novec line of fluids (HFE 7100, etc., sold by 3M(copyright) Corporation) or PF-5060 are among a number of known suitable cooling liquids.
Modern systems using high-dissipation chips frequently have a variety of chips requiring different levels of cooling, only some of which are extreme. Depending on an electronic system""s design, components containing these chips can be located throughout the system. Because they have high dissipation requirements, the chips are not easily cooled using conventional air-cooling. Because the chips are spread out, they are not easily cooled by high-dissipation spray cooling systems, which are typically complex systems. Such cooling systems will typically require either the expense of providing separate components for each individual cooling system, or the expense of interconnecting a group of cooling systems to one or more shared components (e.g., shared pumps, condensers and/or reservoirs). Therefore, high-dissipation cooling systems can be expensive and complicated to implement in complex systems having numerous hot components.
The nozzle design is a key component of spray cooling. Pressure assisted and gas assisted nozzles are known designs. However, these types of nozzles are limited in their ability to control the mass flow rate at which they spray. Therefore, they can cause xe2x80x9cpoolingxe2x80x9d (i.e., a buildup of liquid on the cooled device due to excessive spray rates), which decreases spray cooling effectiveness.
Additionally, pressure-assisted spraying requires one or more high pressure pumps that provide a precise pressure to pump the liquid through a nozzle, even at varying flow rates. Both the distribution and the flow rate of the sprayed liquid can change with variations in the driving pressure and/or small variations in the nozzle construction. Thus, the cooling system is a sensitive and potentially expensive device that can be a challenge to control. Gas atomized spraying requires the delivery of both cooling fluid and a pressurized gas to a spray head in a precise manner. Because the gas must be pressurized separately from the cooling fluid, such systems are not typically closed systems, which invites contamination. Thus, both types of spray cooling system are sensitive and potentially expensive devices that can be a challenge to control.
Furthermore, spray cooling systems rely on both active sprayer systems and active condensing systems to operate. If either system fails, the cooling system likely becomes inoperative, potentially leading to the failure and destruction of the cooled component(s).
Accordingly, there has existed a need for a spray cooling system that can be implemented efficiently and cost effectively in multiple locations in a complex system with high reliability. Various embodiments of the present invention satisfy these and/or other needs, and provide further related advantages.
In various embodiments, the present invention solves some or all of the needs mentioned above by providing a cooling system that efficiently operates on high-dissipation devices using reliable, passive coolant pumps to cycle coolant.
The system is configured for transferring cooling fluid, which has been sprayed by a sprayer head onto a heat source, back up from a pool to the sprayer head. The system features a member extending from the pool to the sprayer head, the member forming a passageway leading from the pool to the sprayer head. The member is configured such that cooling fluid surface tension forces will draw the cooling fluid upward through the passageway from the pool to the sprayer head. Advantageously, the member provides a passive pump that does not require power, a control system or moving parts. It is thus relatively durable and reliable. The system further features a porous material configured to increase the pumping ability of the passive pump.
The system includes a condenser configured to remove heat from vaporized coolant, and a reservoir in fluid communication with the condenser. The reservoir receives coolant that is condensed by the condenser. The system features a structure defining an open passageway extending from the spray chamber to the condenser. The passageway advantageously provides for vaporized coolant to pass to the condenser under gravitational and vapor pressure forces without the need for an active pump.
Other features and advantages of the invention will become apparent from the following detailed description of the preferred embodiments, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. The detailed description of particular preferred embodiments, as set out below to enable one to build and use an embodiment of the invention, are not intended to limit the enumerated claims, but rather, they are intended to serve as particular examples of the claimed invention.